Inspection of Piston and Connecting Rod

Connecting Rod

1. 1
   Check the connecting rod side clearance. Using a feeler gauge, measure the side clearance while moving the connecting rod back and forth. Side clearance Standard: 0.10 - 0.25 mm (0.0039 - 0.0098 in.) Limit: 0.35 mm (0.0138 in.)

   

   A.	If out of specification, install a new connecting rod.

   B.	If still out of specification, replace the crankshaft.

2. 2
   Check the oil clearance of the connecting rod bearing.

   1. Make sure the alignment marks on the connecting rod and cap are aligned to ensure correct assembly.
   2. Remove the 2 connecting rod cap bolts.
   3. Remove the connecting rod cap and bearing half.
   4. Clean the connecting rod journal and bearing.
   5. Place a piece of Plastigage across the connecting rod journal.
   6. Install the bearing half and cap in place, then tighten the bolts.

      Tightening torque: 17.7 - 22 N·m + 78 - 82°

   7. Remove the 2 bolts, the connecting rod cap and the bearing half.
   8. Measure the Plastigage at its widest point.

      Standard oil clearance: 0.033 - 0.051 mm (0.00130 - 0.00201 in.)

      

   9. If the Plastigage is too wide or too narrow, remove the upper bearing half, install a new bearing assembly with the same color code (select the color as shown in the following column), and re-check the clearance.
   10. If the Plastigage shows the clearance is still incorrect, try the next larger or smaller bearing (color listed above or below this one) and check the clearance again. Connecting Rod Marking

       

       Connecting Rod Specifications

       Grade	Mark	Inner Diameter
       a	A	51.000 - 51.006 mm (2.00787 - 2.00811 in.)
       D	B	51.006 ~ 51.012 mm (2.00811 ~ 2.00834 in.)
       c	C	51.012 ~ 51.018 mm (2.00834 ~ 2.00858 in.)

Piston and Rings

1. 1
   Clean the piston

   1. Using a gasket scraper, remove carbon deposits from the top of the piston.
   2. Using a ring groove cleaning tool or a broken piston ring, clean the piston ring grooves.
   3. Using solvent and a brush, thoroughly clean the piston.
2. 2
   The standard outer diameter of the piston is measured 17 mm (0.67 in.) from the top of the piston.

   Standard diameter: 87.970 - 88.000 mm (3.46338 - 3.46456 in.)

   

3. 3
   Calculate the difference between the cylinder bore diameter and the piston diameter.

   Clearance between piston and cylinder: 0.020 - 0.040 mm (0.00079 - 0.00157 in.)

4. 4
   Check the piston ring side clearance. Using a feeler gauge, measure the clearance between a new piston ring and the ring groove wall. Piston ring side clearance Standard No. 1: 0.050 - 0.080 mm (0.00197 - 0.00315 in.) No. 2: 0.040 - 0.080 mm (0.00157 - 0.00315 in.) Oil ring: 0.020 - 0.055 mm (0.00079 - 0.00217 in.) Limit No. 1: 0.100 mm (0.00394 in.) No. 2: 0.100 mm (0.00394 in.) Oil ring: 0.60 mm (0.0236 in.)

   

   If the clearance is greater than the maximum, replace the piston.
5. 5
   Inspect the piston ring end gap. To measure the piston ring end gap, insert the piston ring into the cylinder bore. Position the ring at a right angle to the cylinder wall by carefully pushing it with a piston. Measure the gap with a feeler gauge. If the gap exceeds the service limit, replace the piston ring. If the gap is still too large, recheck the cylinder bore diameter for wear limits. If the bore diameter exceeds the service limit, the cylinder block must be replaced. Piston ring end gap Standard No. 1: 0.15 - 0.25 mm (0.0059 - 0.0098 in.) No. 2: 0.37 - 0.47 mm (0.0145 - 0.0185 in.) Oil ring: 0.20 - 0.50 mm (0.0079 - 0.0197 in.) Limit No. 1: 0.60 mm (0.0236 in.) No. 2: 0.70 mm (0.0275 in.) Oil ring: 0.80 mm (0.0315 in.)

   

Piston Pin

1. 1
   Measure the piston pin diameter.

   Piston pin diameter: 21.997 - 22.000 mm (0.86602 - 0.86614 in.)

   

2. 2
   Measure the clearance between the piston pin and piston. Clearance between piston pin and piston: 0.003 - 0.010 mm (0.00012 - 0.00039 in.)
3. 3
   Check the difference between the piston pin diameter and the connecting rod small end bushing bore. Piston pin to connecting rod interference: 0.005 ~ 0.014 mm (0.00020 ~ 0.00055 in.)